The invention relates to an adaptive transverse equalizer formed of a plurality of time delay elements iteratively connected. Each has a delay time T in accordance with the spacing of two characters sent in succession, and has control elements (coefficients) which are connected to the inputs of a summer. The manipulated variables are derived from the output signal of a decision stage. In an equivalent arrangement, the input signal is applied in parallel to the control elements. The output signals of the control elements are supplied into a delay time chain with a spacing T. Such an equalizer is known, for example, from DT No. 21 33 037 B2.
In digital radio link systems comprising multi-stage quadrature amplitude modulation (for example 16 QAM, 64 QAM, . . .) and a high data rate (140 Mbit/s), adaptive equalizers are employed in the time domain as an effective means against the linear distortions produced by multi-path propagation. Although linear transverse equalizers provided for this purpose have a good acquisition behavior and good convergence properties, these advantages must be weighed off against the unavoidable disadvantages, namely noise boosting due to linear balancing or moderate performance rise, given equalizer extension. Equalizers having quantized feedback (referred to as decision feedback equalizers) exhibit a considerable balancing capability given a low number of coefficients, at least in the case of minimum-phase distortions. Their disadvantage, however, lies in the bearer propagation inherent in recursive systems and in the poorer acquisition properties.